The invention relates, generally, to the outside distribution plants of telecommunications networks and, more particularly, to a method and apparatus for crossconnecting transmission members in the outside distribution plant to create greater flexibility and efficiency in the providing of services to the customer.
It will be appreciated that the typical telecommunications network consists of a plurality of switching systems connected to one another to allow the transmission of signals therebetween. Certain of the switching systems, usually referred to as central office switches, are connected to customer premise equipment (customer line) such as telephones, fax machines, multimedia equipment, personal computers and the like by an outside distribution plant such that the customer lines can communicate with one another via the network.
The outside distribution plant typically consists of optical links connecting the switching systems to remote terminals such as digital loop carriers. One such digital loop carrier is the SLC.RTM. digital loop carrier manufactured and sold by Lucent Technologies Inc. Digital loop carriers function to provide less expensive Loops than copper loops by converting switch interfaces to fiber and back to copper at the remote terminal and consist of an optical remote terminal that interfaces with the optical links from the switching systems. The optical remote terminal connects the optical links to a plurality of line cards where each line card hosts transmission members such as twisted pair distribution lines. A typical digital loop carrier hosts on the order of 800 twisted pair distribution lines where each line card hosts between approximately 1 to 4 of the distribution lines. The twisted pair distribution lines are connected to one of a plurality of feeder distribution interfaces (FDIs). One typical network architecture has four FDIs served by a single digital loop carrier remote terminal where approximately 200 of the 768 twisted pair distribution lines are connected to each of the FDIs. Each FDI connects the 200 twisted pair distribution lines to selected ones of approximately 400 twisted pair customer lines or "drops" that terminate at the customer line on the customer premise. It will be understood that there are approximately twice as many customer lines connecting the FDI to the customer line as there are distribution lines connecting the digital loop carrier to the FDI. This is because typically 2 to 3 customer lines physically connect each customer premise to the FDI even though the usual customer premise has active service on average 1.3 of the lines. Thus, it is not necessary for every customer line to be connected to a distribution line. It has been established, based on average customer usage requirements, that a ratio of two customer lines to every distribution line efficiently and economically services customer needs.
It will also be appreciated that different types of line cards support different types of service. For example, the most common line card supports narrowband service such as POTS service. Other line cards support coin service, ISDN service, broadband service such as asynchronous transfer mode (ATM) carried on one of a family of digital subscriber lines (DSL) and special service such as data port, DC alarm, radio broadcast and other special services. Each line card includes one or more line circuits to which the distribution lines are connected and that control the processing of signals over those lines. Common circuitry is also provided on each line card to control functions common to all of the lines hosted by that line card. It will be understood that common control elements are provided to drive all of the line cards in a remote terminal.
Because different types of line cards support different types of service, it is necessary that each FDI have access to any type of line card that is needed to support any service that will be used by customer lines hosted by that FDI. Thus, any FDI can be connected to narrowband, coin, ISDN, broadband and special line cards in the digital loop carrier hosting that FDI. In the system of the prior art, the distribution lines are hardwired to the line cards such that a predetermined number of the line cards are permanently connected to each FDI. Because the line cards are dedicated to particular FDIs, FDIs cannot share line card resources. As a result, the services that can be delivered to the customer lines hosted by an FDI are limited to the types of services provisioned on the line cards connected to that FDI. Moreover, the need to provide a line card for every service supported by an FDI can waste valuable network resources. For example, to provide ISDN service to one customer, an ISDN line card, capable of hosting up to eight lines, is hardwired to the FDI hosting that customer. If no other customers hosted by that FDI desire ISDN service, up to seven ISDN line circuits remain unused. Such a situation obviously results in an inefficient use of network resources. This problem is exacerbated by the fact that technology and economics are allowing a single line card to host increasing numbers of distribution lines such that the inefficiencies of the existing system will increase.
Similar problems occur in other network architectures. For example, broadband networks such as those that carry asynchronous transfer mode (ATM) traffic include remote terminals such as ATM distribution elements that are similar to the digital loop carrier in that they include line cards that interface between optical links to a host terminal and distribution lines to the FDIs. These distribution elements typically include line cards for carrying broadband traffic or a combination of broadband and narrowband traffic to the customer premise. Like the example of the digital loop carrier discussed above, the line cards of the distribution elements of the broadband network are dedicated to particular FDIs such that network resources are not efficiently utilized.
Thus, an improved method and apparatus for more efficiently distributing line card functionality over the outside distribution plant is desired.